Analysis of the exoplanet containing system Kepler-13     

E.?Budding  M.?D.?RhodesEmail author 《Astrophysics and Space Science》2018,363(3):60

We have applied the close binary system analysis program WinFitter, with its physically detailed fitting function, to an intensive study of the complex multiple system Kepler-13 using photometry data from all 13 short cadence quarters downloaded from the NASA Exoplanet Archive (NEA) (http://exoplanetarchive.ipac.caltech.edu). The data-point error of our normalized, phase-sequenced and binned (380 points per bin: 0.00025 phase interval) flux values, at 14 ppm, allows the model’s specification for the mean reference flux level of the system to a precision better than 1 ppm. Our photometrically derived values for the mass and radius of KOI13.01 are \(6.8\pm0.6~\mbox{M}_{\mathrm{J}}\) and \(1.44\pm0.04~\mbox{R}_{\mathrm{J}}\). The star has a radius of \(1.67\pm0.05~\mbox{R}_{\odot}\). Our modelling sets the mean of the orbital inclination \(i\) at \(94.35\pm0.14^{\circ}\), with the star’s mean precession angle \(\phi_{p}\)—\(49.1\pm5.0^{\circ}\) and obliquity \(\theta_{o}\)\(67.9 \pm 3.0^{\circ}\), though there are known ambiguities about the sense in which such angles are measured.Our findings did not confirm secular variation in the transit modelling parameters greater than their full correlated errors, as argued by previous authors, when each quarter’s data was best-fitted with a determinable parameter set without prejudice. However, if we accept that most of the parameters remain the same for each transit, then we could confirm a small but steady diminution in the cosine of the orbital inclination over the 17 quarter timespan. This is accompanied by a slight increase of the star’s precession angle (less negative), but with no significant change in the obliquity of its spin axis. There are suggestions of a history of strong dynamical interaction with a highly distorted planet rotating in a 3:2 resonance with its revolution, together with a tidal lag of \(\sim30~\mbox{deg}\). The mean precessional period is derived to be about 1000 y, but at the present time the motion of the star’s rotation axis appears to be supporting the gravitational torque, rather than providing the balance against it that would be expected over long periods of time.The planet has a small but detectable backwarming effect on the star, which helps to explain the difference in brightness just after transit and just before occultation eclipses. In assessing these findings it is recognized that sources of uncertainty remain, notably with possible inherent micropulsational effects, variations from other components of the multiple star, stellar activity, differential rotation and the neglect of higher order terms (than \(r_{1}^{5}\)) in the fitting function, where \(r_{1}\) is the ratio of the radius of the star to the mean orbital separation of planet and host star.  相似文献   

Observation and preliminary analysis of a recent Jovian satellite phenomenon     

Allen  W. H.  Budding  E. 《Earth, Moon, and Planets》1986,35(1):73-77

The occultation of Io by Ganymede as observed on 10 June 1985 is reported. The middle of the occultation minimum was found to occur at 14h 14m 5.7s UT. In the plane perpendicular to the line of sight the centres of the two satellite disks passed to within ~ 2530 km of each other, at a relative velocity, in this plane, of about 11 kms^–1. The values of these last two quantities, however, depend on what assumptions are made about the light distribution over io's disk.  相似文献   

Spatially resolved spectrophotometry of comet P/Stephan-Oterma     

Anita L. Cochran  Edwin S. Barker 《Icarus》1985,62(1):72-81

Observations of Comet P/Stephan-Oterma were made with an Intensified Dissector Scanner spectrograph on the McDonald Observatory 2.7-m telescope during the period from July 1980 to February 1981. These spectra cover a range of heliocentric distances from 2.3 AU preperihelion to 1.8 AU postperihelion. A small aperture was used to map the spatial distributions of the gases in the coma. Column densities of the observed cometary emissions (CN, C₃, CH, and C₂) were calculated and it is shown that Stephan-Oterma appeared nearly spherically symmetric. These date are used by Cochran (1985, Icarus62, 82–92) to constrain chemical models of Stephan-Oterma.  相似文献   

Martian great dust storms: Interpretive axially symmetric models     

Edwin K. Schneider 《Icarus》1983,55(2):302-331

The simplified theory of steady, nearly inviscid, thermally forced axially symmetric atmospheric motions developed by Schneider (1977) is applied to the study of the problem of the Martian great dust storms. A highly idealized calculation of the atmospheric response to heating concentrated in a small latitude band is carried out. Qualitatively different local and global response regimes are identified. As the heating is increased from zero, some critical value is reached at which the response jumps from local to global. It is suggested that this transition from local to global response may be related to the observed explosive growth of great dust storms. Results from the idealized model indicate that subtropical latitudes are favored for the initiation of a dust raising global dust storm, as the meridional scale of the response to a heat source of fixed intensity is largest for the heat source located close to the equator, but the surface stress in the zonal direction produced by the response increases as the heat source is moved towards the poles. Also, the steady axially symmetric Martian response to solar forcing is examined. Modification to the solar forced response due to an added latitudinally localized heat source is briefly discussed, and it is indicated that similar transition behavior to that obtained in the more idealized model is to be expected in this case also. Implications of the dynamical model for the dependence of the occurence of great dust storms on orbital parameters are remarked on.  相似文献   

Thermal history of the unsaturated zone at Yucca Mountain,Nevada, USA     

Joseph F. Whelan  Leonid A. Neymark  Richard J. Moscati  Brian D. Marshall  Edwin Roedder 《Applied Geochemistry》2008

Secondary calcite, silica and minor amounts of fluorite deposited in fractures and cavities record the chemistry, temperatures, and timing of past fluid movement in the unsaturated zone at Yucca Mountain, Nevada, the proposed site of a high-level radioactive waste repository. The distribution and geochemistry of these deposits are consistent with low-temperature precipitation from meteoric waters that infiltrated at the surface and percolated down through the unsaturated zone. However, the discovery of fluid inclusions in calcite with homogenization temperatures (T_h) up to ∼80 °C was construed by some scientists as strong evidence for hydrothermal deposition. This paper reports the results of investigations to test the hypothesis of hydrothermal deposition and to determine the temperature and timing of secondary mineral deposition. Mineral precipitation temperatures in the unsaturated zone are estimated from calcite- and fluorite-hosted fluid inclusions and calcite δ¹⁸O values, and depositional timing is constrained by the ²⁰⁷Pb/²³⁵U ages of chalcedony or opal in the deposits. Fluid inclusion T_h from 50 samples of calcite and four samples of fluorite range from ∼35 to ∼90 °C. Calcite δ¹⁸O values range from ∼0 to ∼22‰ (SMOW) but most fall between 12 and 20‰. The highest T_h and the lowest δ¹⁸O values are found in the older calcite. Calcite T_h and δ¹⁸O values indicate that most calcite precipitated from water with δ¹⁸O values between −13 and −7‰, similar to modern meteoric waters.  相似文献   

Robust Range-Only Beacon Localization   总被引：2，自引：0，他引：2  

Edwin Olson John J. Leonard Seth Teller 《Oceanic Engineering, IEEE Journal of》2006,31(4):949-958

In this paper, we present a system capable of simultaneously estimating the position of an autonomous underwater vehicle (AUV) and the positions of stationary range-only beacons. Notably, our system does not require beacon positions a priori, and our system performs well even when range measurements are severely degraded by noise and outliers. We present a powerful outlier rejection method that can identify groups of range measurements that are consistent with each other, and a method for initializing beacon positions in an extended Kalman filter (EKF). We have successfully applied our algorithms to real-world data and have demonstrated a simultaneous localization and mapping (SLAM) system whose navigation performance is comparable to that of systems that assume known beacon locations  相似文献   

Cloning of a chub metallothionein cDNA and development of competitive RT-PCR of chub metallothionein mRNA as a potential biomarker of heavy metal exposure   总被引：3，自引：0，他引：3  

Hayes RA  Regondi S  Winter MJ  Butler PJ  Agradi E  Taylor EW  Kevin Chipman J 《Marine environmental research》2004,58(2-5):665-669

Metallothionein has been assayed in a range of aquatic animal tissues as an indicator of metal exposure. We sequenced chub (Leuciscus cephalus) metallothionein cDNA which showed over 90% homology to common carp, goldfish and stone loach and 77% homology to rainbow trout sequences for metallothionein. We then used the extended primer method to develop an accurate quantitative competitive RT-PCR assay for metallothionein mRNA. RT-PCR was used to measure metallothionein mRNA in feral chub from a range of field sites, with different levels of heavy metal pollution, in the West Midlands, UK. Measurements were complemented by analysis of liver and gill metallothionein protein by capillary electrophoresis. There was no significant difference in the metallothionein protein levels between fish of different rivers and there was no evidence of elevation of mRNA at the sites of highest metal exposure. The level of metal exposure (e.g. zinc, nickel and cadmium each ranging between 15 and 28 microg/l ) at the pH (7.5-8.5) of these rivers appears insufficient to elevate hepatic or gill metallothionein in chub. A lack of elevation of hepatic metallothionein mRNA in chub exposed to zinc, copper and manganese for 24 h and 10 days in the laboratory also suggests a non-responsiveness of this species.  相似文献   

Effect of native and invasive cordgrass on Macoma petalum density, growth, and isotopic signatures   总被引：1，自引：0，他引：1  

Elizabeth D. Brusati  Edwin D. Grosholz 《Estuarine, Coastal and Shelf Science》2007,71(3-4):517-522

Ecosystem engineers can influence community and ecosystem dynamics by controlling resources, modifying the flow of energy or biomass, or changing physical characteristics of the habitat. Invasive hybrid cordgrass (Spartina alterniflora × Spartina foliosa) is an ecosystem engineer in salt marshes in San Francisco Bay, California, U.S.A. that raises intertidal elevations and may be either increasing C₄ plant carbon input into food webs or tying up carbon in a form that is not usable by consumers. A manipulative experiment compared abundance, growth, and stable isotope (δ¹³C and δ¹⁵N) composition of the clam Macoma petalum (=M. balthica) among native marsh, hybrid Spartina, and mudflats in central San Francisco Bay. We found higher densities (individuals m⁻²) of M. petalum on mudflats compared to either native or hybrid Spartina (p < 0.001). Macoma petalum shell growth was significantly greater in mudflats than in either vegetation type in 2002 (p = 0.005) but not 2003. Differences in shell growth between native and hybrid Spartina were not significant. Stable isotope results showed differences between habitats in δ¹³C but not δ¹⁵N. Carbon signatures of M. petalum placed in Spartina were much more depleted than the isotopic signature of Spartina. Neither native nor hybrid Spartina appears to be a significant carbon source for M. petalum in San Francisco Bay, and we found no evidence that hybrid Spartina contributes carbon to M. petalum beyond what is provided by S. foliosa, despite the hybrid's much greater biomass. Our results show that loss of mudflat habitat, rather than increased input of C₄ carbon, is the greatest effect of the invasion of hybrid Spartina on M. petalum.  相似文献   

Stellar populations as a function of radius in giant elliptical galaxies     

Reynier F. Peletier  Edwin A. Valentijn 《Astrophysics and Space Science》1989,156(1-2):127-131

Accurate surface photometry has been obtained inJ andK for 12 giant elliptical galaxies. Ellipses have been fitted, to obtain luminosity, ellipticity, and major axis position angle profiles. The results have been combined with visual profiles from CCD observations. We find that elliptical galaxies become bluer inV - K on the average by 0.3 (mag/sq xr _e) going outward from the nucleus. Radial colour gradients inV - K correlate strongly with those inU - V andB - V. By modelling, using theoretical isochrones, it is found that the observed colour gradients can be explained by a gradient in metallicity, if in addition the proportion of hot stars rises very rapidly with decreasing metallicity.  相似文献   

The Potential of Maps APIs for Internet GIS Applications   总被引：2，自引：0，他引：2  

T Edwin Chow 《Transactions in GIS》2008,12(2):179-191

Since the launching of Maps Application Programming Interfaces (APIs) in 2005, many web developers, including geographers and non‐geographers, applauded the freely adaptable tools and used them to spawn numerous Internet applications. The success of the Maps APIs is largely attributable to its no‐cost policy, the availability of global data coverage, dynamic navigation, query capability, and ease of implementation. Despite its versatility in dynamic exploration of geographic data online, the existing Maps APIs lack Geographic Information System (GIS) functionalities compared to other Internet Mapping Services. The goal of this research was to review the potential of the Maps APIs for Internet GIS applications. This research employed the Google Maps API and developed a web prototype that disseminates spatial information of urban sprawl in Mundy Township, Michigan. The results revealed that both vector and raster data could be effectively represented by using the Maps API. Moreover, the Geographic Markup Language (GML) approach illustrated great potential for developing Internet GIS solutions around open specifications. This research suggested several potential solutions to expand the spectrum of GIS operations of the Maps APIs by incorporating the XML‐related technology and extending the JavaScript library.  相似文献